[U-Boot] [PATCH] spi: mxc: Fix data loss for non aligned write buffers.

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Jagan,

On Wed, 16 Oct 2013 11:16:49 +0530, Jagan Teki
<jagannadh.teki@gmail.com> wrote:

> Hi,
> 
> On Tue, Oct 15, 2013 at 11:27 PM, Martin Fuzzey <mfuzzey@parkeon.com> wrote:
> > When writing buffers that are not 32 bit aligned data loss occurs.
> >
> > This can also occur when the total transfer size is not a multiple of 4 bytes
> > since the extra bytes are written first causing the rest to be unaligned.
> >
> > This can be seen by writing to SPI flash a 57 byte file containing 00 01 .. 38:
> >
> > U-Boot > dhcp data.bin
> > ...
> > Bytes transferred = 57 (39 hex)
> > U-Boot > md.b $loadaddr
> > 72000000: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f    ................
> > 72000010: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f    ................
> > 72000020: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f     !"#$%&'()*+,-./
> > 72000030: 30 31 32 33 34 35 36 37 38 ff ff ff ff ff ff ff    012345678.......
> > U-Boot > sf write $loadaddr 0 $filesize
> >
> > U-Boot > mw.b $loadaddr ff 100
> > U-Boot > sf read $loadaddr 0 100
> > U-Boot > md.b $loadaddr
> > 72000000: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f    ................
> > 72000010: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f    ................
> > 72000020: 20 21 22 23 24 29 2a 2b 2c 31 32 33 34 ff ff ff     !"#$)*+,1234...
> > 72000030: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
> >
> > [bytes 25-28, 2d-30, 35-38 are missing]
> >
> > Activating debug in the write command gave:
> > spi_xchg_single: bitlen 256 dout 0x72000000 din 0x0
> > Sending SPI 0x10203
> > Sending SPI 0x4050607
> > Sending SPI 0x8090a0b
> > Sending SPI 0xc0d0e0f
> > Sending SPI 0x10111213
> > Sending SPI 0x14151617
> > Sending SPI 0x18191a1b
> > Sending SPI 0x1c1d1e1f
> > SPI Rx: 0xffffffff 0xffffffff
> > ...
> > SPI Rx: 0xffffffff 0xffffffff
> > spi_xchg_single: bitlen 200 dout 0x72000020 din 0x0
> > Sending SPI 0x20
> > Sending SPI 0x21222324
> > Sending SPI 0x292a2b2c  <===  What happened to 25262728?
> > Sending SPI 0x31323334
> > Sending SPI 0xffffffff
> > ...
> > SF: program success 57 bytes @ 0x0
> Thanks for your log, for showing the exact issues.

Agreed, but I think this log could go in a comment below the '---'
line, so that the commit message focuses on describing what the patch
does, rather than how it was found out necessary.
 
Amicalement,
-- 
Albert.